I came upon this translation in a lesson and typed in "Yo como desayuno" I now realize that 'desayuno' is also a verb and if como is to be used, the translation must be 'yo como el desayuno', the 'el' clarifying the fact that 'desayuno' is to be seen as a noun meaning 'breakfast'. Another correct translation would be 'Yo desayuno' with 'desayuno' acting as a verb meaning 'I eat breakfast'.
Is 'desayuno' the only word that can be a verb or a noun or are there others?
there are many others. The basic form of the verb is "desayunar" - "yo desayuno" is the conjugation (yo/I) of the verb. short examples: yo recuerdo (verb recordar) - el recuerdo (noun) ella cena (verb cenar) - la cena (noun)
Also "ceno" is a verb that comes from "cena" (dinner). So "Yo ceno" would mean "I eat dinner"
Lunch and dinner work the same way. They say almorzar( to have lunch) and cenar (to dine). Also, almuerzo is lunch and cena is dinner.
One can also "breakfast" and "lunch" in English. (Generally, one would say something like "I breakfasted on eggs," rather than using the verb in isolation.) Those expressions are a bit archaic, but not outrageously so.
Spanish is a lot like English in the sense that there are many nouns that can double as verbs. With desayuno it can mean a breakfast itself or the act of having breakfast. A lot like how in English party can mean a party itself or the act of partying.